Circadian Rhythm in Activity of Lympholytic Natural Killer Cells from Spleens of Fischer Rats

Open Access
Publisher Website
Google Scholar
Abstract
Three and one-half-week-old male inbred Fischer rats housed individually at 24 ± 1°C with Purina Chow and water ad libitum were randomly assigned to six different rhythmometry chambers, each lighted daily for 12 hr and darkened the following 12 hr. The timing of these regimens differed from one chamber to the next by 4 hr (i.e., one chamber was illuminated from 0600 to 1800, the next from 1000 to 2200, etc.). Thus, completely light-dark synchronized animals sampled from the six chambers at any given clock time were intended to represent, in relation to the onset of the daily light span, six different circadian stages, differing from each other by 4 hr. After 2-week standardization in the chambers, rectal temperature was measured and the animal killed, its spleen collected aseptically in RPMI 1640 medium containing 10% fetal calf serum, and the activity of natural killer (N.K.) cells determined in a direct 51Cr release assay. Spleen cells of 6-week-old rats were effector cells and RL♀1 mouse lymphoma cells in tissue culture were target cells. Two experiments carried out, each on 3 successive days in November 1977 and February 1978, using subtotals of 24 rats at each lighting stage; i.e., a total of 144 rats for six intended circadian stages, revealed by cosinor analysis a circadian rhythm in N.K. cell activity and rectal temperature. The circadian recetal temperature acrophase may be a marker with similar timing of high murine N.K. cell activity. In the context of a budding chronoimmunology, these findings extend the scope of a spectrum of bioperiodic neuroendocrine influences on lymphoid activity and body resistance.